February 10, 2014

How Do Polar Bears Keep Warm? It May Be In Their Genes

During the recent polar vortex that swept down into the US, even polar bears in the Chicago zoo had to go inside. However, new research gives more insight into how these animals' Arctic counterparts are able to keep warm in extremely low winter temperatures.

The reason the Chicago polar bears had to venture indoors during the deep freeze is due to a diet that is much different from polar bears that live in the Arctic tundra. The latest study shows how these Arctic polar bears utilize genetic adaptations and nitric oxide to stay warm.

“With all the changes in the global climate, it becomes more relevant to look into what sorts of adaptations exist in organisms that live in these high-latitude environments,” lead researcher Charlotte Lindqvist, PhD, University of Buffalo assistant professor of biological sciences, said in a statement.

For the study, the team analyzed the mitochondrial and nuclear genomes of 23 polar bears, three brown bears and a black bear. The team wrote in the journal Genome Biology and Evolution that nitric oxide production in the polar bear genome contains genetic differences from comparable genes in brown and black bears.

The more southerly bear species are able to survive the winter through hibernation, helping to conserve the energy and keep warm. However, the difference in how nitric oxide is controlled shows how much different polar bears really are than their darker-colored cousins.

“This study provides one little window into some of these adaptations,” Lindqvist said in a statement. “Gene functions that had to do with nitric oxide production seemed to be more enriched in the polar bear than in the brown bears and black bears. There were more unique variants in polar bear genes than in those of the other species.”

The genetic adaptations discovered are important because it unveils the role that nitric oxide plays in energy metabolism. Cells typically transform nutrient into energy, but adaptive thermogenesis cells produce heat instead of energy in response to a particular diet or environmental conditions.

Nitric oxide production could be a key switch triggering how much heat or energy is produced as cells metabolize nutrients.

“At high levels, nitric oxide may inhibit energy production,” Andreanna Welch, of Durham University and first author of the paper, said in a statement. “At more moderate levels, however, it may be more of a tinkering, where nitric oxide is involved in determining whether — and when — energy or heat is produced.”